To Dam or Not To Dam

To Dam or Not To Dam


The dam failure in the Marquette area brings up, once again, the issue of whether dams ought to be on rivers at all. Although the placement of any dam needs to be reviewed on a case-by-case basis, there are many arguments against having dams.


  • Reduce river levels, affecting healthy instream ecosystems
  • Block rivers, preventing the flow of nutrients, impeding the migration of fish and other wildlife, and blocking recreational use.
  • Slow rivers. Many fish species, such as salmon, depend on steady flows to flush them downriver early in their lives and guide them upstream to spawn. Reservoirs disorient fish and significantly increase the length of their migration.
  • Alter water temperatures. By slowing water flow, most dams increase water temperatures. Others decrease temperatures by releasing cooled water from the bottoms of reservoirs. Fish and other species are sensitive to these temperature irregularities, which frequently destroy native, and often rare, populations.
  • Alter timing of flows, cause reservoir levels to fluctuate, and decrease oxygen levels in the waters (when oxygendeprived water is released from behind a dam, it can kill fish and vegetation downstream).
  • Hold back silt, debris, and nutrients. By slowing flows, dams allow silt to collect on river bottoms and bury spawning habitat. Silt trapped above dams can accumulate heavy metals and other pollutants. Dams also trap gravel, logs, and other debris, eliminating their potential use down stream as sources of valuable food and habitat.
  • Both the River Alliance of Wisconsin (GLAHNF Advisors), and Wisconsin Wetlands Association (GLAHNF WI Hub) have excellent information on this topic if you want to contact them.


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Images courtesy of Steven Huyser-Honig,
West Grand Boulevard Collaborative, & Yellow Dog Watershed Preserve.